# Total differential

## Homework Statement

For:
z(x,y)=(x^2)y-3y
Find $$\Delta$$z and dz when x=4, y=3, $$\Delta$$x=-0.01, $$\Delta$$y=0.02

## The Attempt at a Solution

I got the partial derivatives:

df/dx=2xy, and df/dy=x^2-3

and solved dz=0.02

However, I don't know how to find $$\Delta$$z

## Answers and Replies

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